I'm unsure how to answer the question because I don't believe in christening, I think everything has been covered though about the fact you're not a Christian and don't seem to have any reason for having a Christening - no party, don't need it for school, it's not your faith...
My children are Dedicated with godparents who aren't necessarily Christian and no question about whether they were christened because our denomination doesn't believe in it. We chose godparents as people we thought would be there for the children and support them, not to teach them about the faith, that's our job. We believe baptism is for believers and is not the way to Heaven, it's just a step of faith and a public declaration as John the Baptist used it.
I find some of the comments about you can't be a practising Christian if you are not christened incredibly insulting! I was Dedicated, my parents thanked God for me, they bought me up going to church regularly and teaching me about the Christian faith (nothing was forced on us or anything, my brother doesn't go to church or even live a Christian life, that was the choice we all made and our parents left us free to do that) when I was old enough to understand and want to do it I accepted Jesus as my saviour. A little older still I was baptised, Biblical baptism where you enter water and are taken under until completely covered by it. Everything was my choice, me being obedient to the word, not something thrust on me by parents wanting a booze up and pretty pictures. How am I less of a practicing Christian than the person not been in church since their parents knees up when they were a baby?
"Baptists are the exception"
No, they're not. There are many denominations that don't believe in infant baptism.
"Does it make it any better that my children are aged 3 and 4 years old"
Not really. My 4 year old is very bright, she goes to a CoE school and Sunday School each week. Over Easter she has realised that we're Christians and keeps telling me things she has learnt at school, always ended with "that's what Christian's believe and we're Christians so I know" you can guarantee she's never quite right with what she's saying. She is surrounded by the Christian faith and wouldn't understand how to give her life to Jesus, how do you expect younger children brought up in an agnostic family to know better?
"Are there also a wedding crowd and funeral crowd?"
You should try hanging around in wedding forums for awhile! I'm always amazed at the people who choose their church based on how pretty the pictures are then complain about the cost, the pre-marriage course, having to go to church for however long and ask how they stop strangers coming to their wedding.